External spring needle valve fuel injector



Oct. 1, 1968 K. L. HULSING Filed March 5, 1967 1 59 g N j z. ,1 H

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INVENTOR. Xemezf/z [I Hit/S1129 BY ATORNEY United States Patent 3,403,632 EXTERNAL SPRING NEEDLE VALVE FUEL INJECTOR Kenneth L. Hulsing, Plymouth, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 3, 1967, Ser. No. 620,310 4 Claims. (Cl. 103-154) ABSTRACT OF THE DISCLOSURE A unit type fuel-injector pump having a needle-type injection valve openable oppositely of the direction of fuel flow and biased closed by a spring surrounding the spacer block in which the valve is slidably guided, the spring force being transmitted to the valve by a cross pin extending through a transverse slot in the spacer block.

Background of the invention This invention relates to fuel injection apparatus and particularly to unit type fuel injector-pumps for diesel engines.

Devices of this type are well known, including those wherein the normally closed injection valve is of the needle type which opens oppositely of the direction of fuel flow during injection. The construction disclosed in US. Patent No. 3,006,556 to Shade et al. is typical thereof. In such previous injector-pumps, the spring which biases the needle valve to its closed position has been centrally located in a relatively small diameter spring chamber where it directly acts against the needle valve. In such arrangements, the tip passage through which the injection fuel is delivered from the pump chamber to the spray tip outlet is formed by a series of connecting drilled passages through the spacer elements outboard of this central spring chamber. As a result, the limited space available in the spring chamber has placed severe limitations on the size and consequent strength of the injection valve spring, adversely affecting its cost and durability because of the high stressing of the spring in operation.

Summary of the invention In accordance with the invention, I have overcome the above-mentioned problems and disadvantages of such needle type unit injector-pumps by an arrangement which enables use of a much larger than conventional valve spring, and which also enables shortening and thereby reducing the volume required for the tip passage for better volumetric efiiciency of injection. By substituting a spring which externally surrounds the spacer parts of the nozzle, heavier and stiffer material can :be employed for the spring, and its biasing action on the needle valve can be very simply effected by means of a transfer pin loosely disposed within a cross slot in the spacer.

These and other objects and advantages of the invention will be better understood from the following description, having reference to the attached drawing.

Brief description of the drawing FIGURE 1 is a longitudinal sectional view through a unit injector-pump constructed in accordance with the invention.

FIGURE 2 is an enlarged view of the lower portion of the unit shown in FIGURE 1.

FIGURE 3 is a further enlarged view, similar to FIG- URE 2 but showing a slight modification of the invention.

Description of the preferred embodiment Referring now in detail to the drawing, and first to FIGURES 1 and 2, the upper portion of the unit is con- 3,403,632 Patented Oct. 1, 1968 lCC ventional and comprises a housing 1 in which a plunger 2 is reciprocable. Forming an extension of and threaded to the lower end of the housing 1 is a nut 3 enclosing a bushing 4 which forms the pump cylinder for the plunger. An annular reservoir space 5, surrounding the bushing within the nut, is supplied with fuel via passages 6 in the housing from an external fuel connection 7. The plunger has the usual external metering groove 8 adjacent its lower end by which opening and closing of ports 9 and 10 in the bushing are controlled during each downward stroke of the plunger to handle a predetermined volume of fuel via the spray orifices 11 in the lower end of the spray tip 12. Other details of the upper or pump part of the unit are also conventional and require no description for present purposes.

As will be seen best in FIGURE 2, the flanged upper end 13 of the spray tip seats in the lower end of the nut 3, being clamped thereagainst by spacer means comprising a lower spacer block 14 and an'upper spacer block 15, which latter abuts against the lower end of the bushing 4. The spray tip has its outlet 16 normally closed by a needle type injection valve 17 whose upper end terminates in a shaft portion 18 above the upward end of the spray tip. Intermediate its ends the needle valve has an enlarged or piston portion 19 which has a close sliding fit in the upper bore 20 of the spray tip. Surrounding this piston portion of the valve within the spray tip is a fuel chamber 21 which extends down to the 'spray tip outlet 16 and is connected through the upper end of the spray tip via one or more drilled passages 22. These latter passages communicate, in turn with an annular groove 23, in the bottom face of the lower spacer block 14. A similar groove 24 is shown in the upper end face of this spacer 14, and is connected with the groove 23 by one or more drilled passages 25 through this spacer. The upper spacer 15 is shown provided with a fuel cavity 26 which is connected with the groove by one or more drilled passages 27. Disposed within the cavity 26 is a check valve 28 in the form of a flat plate, which normally rests in its open position (shown) on a central protuberance 29 in the bottom of the cavity, but which is raisable in response to fuel pressure to close against the lower end of the bushing 4. It will be appreciated that the passages 27, 25 and 22 provide for flow of fuel from the pump chamber 30 in the bushing to the spray tip outlet 16, and that the check valve 28 serves to block any reverse flow of fuel as might be induced by engine combustion gases entering these fuel passages in the event the needle valve 17 failed to close after an injection.

The injection valve is biased to its closed position by spring means shown in the form of a coil compression spring 31 surrounding the spacer 14. This spring reacts upwardly, through its seat formed by the upper spacer 15, against the lower end of the bushing 4. The lower end of the spring is provided with a retainer 32 which slidably embraces the lower spacer 14. An opening 33 is provided in the lower end of the spacer 14 to loosely receive the shaft portion 18 of the needle valve, and intersecting this opening is a cross slot 34 in which a pin 35 is loosely disposed. Intermediate its ends, this pin abuts the upper end of the needle valve shaft portion 18, and the opposite ends of the pin extend into close fitting openings 36 in the retainer 32. The upper wall 37 of the cross slot serves as a stop to limit opening movement of the needle valve.

During operation, as fuel pressure is built up in the pumping chamber 30 by the plunger 2 moving downward to close the bushing ports 9 and 10, corresponding fuel pressure builds up in the fuel chamber 21 below the piston portion 19 of the valve sufilcient to raise it to open the outlet 16 for injection of fuel through the spray tip ori- 3 fices 11. Such. upward movement of the needle'valve is transmitted by the pin 3.5 to the spring retainer 32 and against the underside of the spring 31. The spring force thus opposes such opening movement of the needle valve in accordance with the amount of fuel pressure developed in the pump chamber 30 and fuel chamber 21, and when this pressure is relieved by the plunger metering groove 8 uncovering the bushing port 9 at the end of the injection stroke the needle valve again returns to its closed position.

The modification shown in FIGURE 3 differs principally from that previously described in that the needle valve 17 has its piston portion 19' slida bly guided within a bore 20' in the lower spacer member 14', instead of in the spray tip 12'. An O-ring type of seal 38 is carried by this piston portion of the needle valve to effect av good seal against leakage of fuel into the cross slot 34'. Also, the needle valve return spring 31 seats at its upper end against a retainer 39 instead of against the upper spacer 15', and the anti-blow back valve 28' is arranged to close against this upper spacer instead of against the lower end of the pump bushing 4. The operation of this form of the invention is, however, substantially identical with that of FIGURES 1 and 2.

While the invention has been shown and described with reference to only two embodiments, it is appreciated that various minor changes in the parts and their relationship may be made without departing from the spirit and scope of the invention as hereinafter defined.

I claim:

1. In a unit fuel injector-pump, a plunger, a member defining a pumping chamber for said plunger, a spray tip having an outlet for fuel displaced from the chamber by the plunger, spacer means between said member and spray tip, said spacer means having a passage therethrough for fuel flow from the chamber to the tip,

, an injection valve normally closing said outlet but movable toward said member to open the outlet in response to a predetermined fuel pressure in the passage, said spacer means having a cross-slot extending transversely thetethrough, spring means disposed externally of the spacer means and reacting against said member, and a pin loosely disposed in said cross-slot and interconnecting. the spring and injection valve for biasing saidvalve closed.

2. The invention of claim 1, wherein said injection valve includes a shaft portion extending into said crossslot and the pin overlies the extended end of said shaft portion.

3. The invention of claim 2, including a retainer for said spring means, said retainer having a slida'ble fit on the spacer means and openings closely receiving the respective ends of the pin.

4. The invention of claim 3, wherein said cross-slot has a wall abuttable by the pin to limit opening movement of the injection valve.

References Cited UNITED STATES PATENTS 2,279,010 4/1942 NiChOls 239---92 X 2,371,787 3/1945 Ward 239-438 X 2,496,804 2/1950 Meitzler 2,556,171 6/1951 Dudek. 2,985,378 5/1961 Falberg. 3,006,556 10/1961 Shade et a1. 239-88 3,115,304 12/1963 Humphries. 3,190,561 6/1965 Fuller Ct 211.

FRED C. MATTERN, 1a., Primary Examiner.

W. J. KRAUSS, Assistant Examiner. 

